Anti-overpressure fuel tank

ABSTRACT

A fuel tank with a venting system includes a flap for closing and opening a vent made in the tank. The flap is coupled to a float. The flap includes a valve coupled to a second float mounted in a hinged manner in the tank so that the valve adopts a closed position, being pushed by the second float when the level of fuel in the tank reaches a certain threshold, and an open venting position in order to prevent overpressure within the tank, being driven by the second float when the level of fuel is below the threshold and the force exerted by the internal pressure on the valve is less than the sum of the forces exerted on the valve by the atmospheric pressure and by the weight of the second float.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority to and thebenefit of co-pending U.S. provisional patent application Ser. No.15/545,090, ANTI-OVERPRESSURE FUEL TANK, filed Jul. 20, 2017,PCT/FR2016/050085, filed Jan. 18, 2016, and FR 1550916, filed Feb. 5,2015, all of which applications are incorporated herein by reference inits entirety.

FIELD OF THE APPLICATION

The application relates to fuel tanks, particularly it concerns a fueltank equipped with a venting system.

BACKGROUND

A fuel tank, of an aircraft for example, can be equipped with a ventingsystem of the type comprising a flap for equalization of the internalpressure of the tank and the atmospheric pressure.

SUMMARY

A fuel tank with a venting system includes a flap for closing andopening a vent made in the tank. The flap is coupled to a float and ismounted in a hinged manner in the tank so as to adopt a closed position,being pushed by the float when the level of fuel in the tank reaches acertain threshold, and an open venting position, being driven by thefloat when the level of fuel is below the threshold. The flap includes avalve coupled to a second float mounted in a hinged manner in the tankso that the valve adopts a closed position, being pushed by the secondfloat when the level of fuel in the tank reaches a certain threshold,and an open venting position in order to prevent overpressure within thetank, being driven by the second float when the level of fuel is belowthe threshold and the force exerted by the internal pressure on thevalve is less than the sum of the forces exerted on the valve by theatmospheric pressure and by the weight of the second float.

The second float can be subjected to the valve by means of an armforming a lever in order to increase the force exerted by the secondfloat on the valve.

An anti-overpressure fuel tank includes a tank. A venting system of thetank includes a float mounted in a hinged manner in the tank. A flap ismechanically coupled to the float. The flap closes an opening in thetank in a closed flap position. A valve is disposed in the flap. Thevalve is mechanically coupled to a second float mounted in a hingedmanner in the tank. The valve includes an open valve position to open anorifice in the flap and a closed valve position to close the orifice inthe flap. The valve adopts a closed position, being pushed by the secondfloat when the level of fuel in the tank reaches a certain threshold.The valve adopts an open venting position during the closed flapposition in order to prevent overpressure within the tank, being drivenby the second float when the level of fuel is below the threshold andthe force exerted by the internal pressure on the valve is less than thesum of the forces exerted on the valve by the atmospheric pressure andby the weight of the second float.

The second float can be coupled to the valve by means of an arm forminga lever in order to increase the force exerted by the second float onthe valve.

The foregoing and other aspects, features, and advantages of theapplication will become more apparent from the following description andfrom the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the application can be better understood with referenceto the drawings described below, and the claims. The drawings are notnecessarily to scale, emphasis instead generally being placed uponillustrating the principles described herein. In the drawings, likenumerals are used to indicate like parts throughout the various views.

FIG. 1 is a schematic representation illustrating a first embodiment ofthe invention, the valve being controlled by a spring; and

FIG. 2 is a schematic representation illustrating a first embodiment ofthe invention, the valve being controlled by a second float.

DETAILED DESCRIPTION

The present invention concerns the technical domain of fuel tanks, of anaircraft for example, and more particularly it concerns a fuel tankequipped with a venting system for equalizing the internal pressure ofthe tank to atmospheric pressure, as a function of fuel consumption, inorder to prevent any overpressure within said tank.

The invention finds particularly advantageous application in a fuel tanksubjected to an inerting system by means of the injection of an inertgas.

Known from the prior art is a fuel tank, of an aircraft for example,equipped with a venting system of the type comprising a flap for closingan opening to the exterior made in the tank. In particular, the flap issubjected to a float, and is mounted in a hinged manner within the tankso as to adopt a closed position, pushed by the float when the level offuel in the tank reaches a certain threshold, and an open ventedposition, driven by the float when the level of fuel is below saidthreshold.

In other words, during the phase of filling the fuel tank, the floatvalve remains open until the level of fuel, which is increasing, pushesthe float and drives the flap in order to close the opening of the tank,making it possible to prevent fuel from being evacuated from the tankthrough said opening. Subsequently, in flight, and more particularly infuel consumption phase, the level of fuel decreases so that the floatdrives the flap open by the effect of gravity, so that the flap adoptsthe open vented position and enables, by admission of exterior air,equalization of the internal pressure of the tank and the atmosphericpressure.

However, this type of tank, equipped with a venting system, has certaindisadvantages inherent to the structure thereof.

Indeed, the movements of the fuel inside the tank, for example duringpitching a rolling of an aircraft comprising such a tank, can cause, byaction on the float, undesired closing of the flap. In particular, thisis a major disadvantage when said tank is subjected to an inertingsystem by means of the injection of an inert gas. Indeed, in the domainof aeronautics, and in order to meet the new requirements concerningaircraft safety, and more particularly to avoid the risks offlammability of the mixture of air and fuel vapor in the tanks, thetanks are subjected to inerting systems, active under some conditions,such as for example when the oxygen content in the tank exceeds acertain threshold. Thus, the injection of inert gas while the flap isunintentionally closed causes the pressurization of the tank, whichpressure maintains the flap in the closed position, even when the fuelis no longer exerting force on the float.

The result is that the venting function of the tank is no longerensured, and the pressure increases inside the tank, which can havedisastrous consequences.

One of the purposes of the invention, therefore, is to remedy thesedisadvantages by proposing a fuel tank equipped with a venting system,which is safe and which makes it possible to ensure—optimally and inevery circumstance—the venting function of said tank, in order to avoidany overpressure within said tank.

To that end, a fuel tank has been developed comprising a venting systemcomprising a flap for closing an opening made in the tank. The flap issubjected to a float, and is mounted in a hinged manner in the tank soas to adopt a closed position, pushed by the float when the level offuel in the tank reaches a certain threshold, and an open ventedposition, driven by the float when the level of fuel is below saidthreshold.

The flap comprises a valve controlled by means capable of opening thevalve when the flap is in the closed position while the level of fuel isbelow said threshold, in order to prevent overpressure within said tank.

In this way, when the flap is undesirably maintained in the closedposition by the force exerted by internal pressure, the venting functionof the tank is ensured by the valve. Thus, the tank according to theinvention is safe.

According to a first embodiment of the tank according to the invention,the valve is in the form of a rod mounted sliding within an orifice ofthe flap, between a position of opening and a position of closing theorifice. The rod comprises a first end with a shoulder intended to actas a stop for the closed position of the rod, and a second end with ashoulder forming a seat for a compression spring arranged around the rodand pressed against the flap in order to maintain the rod in the closedposition. Thus, when the force exerted by the internal pressure on thevalve exceeds the sum of the forces exerted on the valve by theatmospheric pressure and the spring, said valve is pushed into the openposition, against said spring, and ensures venting of the fuel tank inorder to prevent overpressure within said tank.

According to a second embodiment of the tank according to the invention,the valve is subjected to a second float and mounted in a hinged mannerin the tank such that said valve adopts a closed position, by beingpushed by the second float when the level of fuel in the tank reaches acertain threshold, and an open vented position in order to preventoverpressure within said tank, by being driven by the second float whenthe level of fuel is below said threshold and the force exerted by theinternal pressure on the valve is less than the sum of the forcesexerted on the valve by the atmospheric pressure and by the weight ofthe second float.

Advantageously, in this embodiment, the second float is subjected to thevalve by means of an arm forming a lever arm for augmenting the forceexerted by the second float on the valve.

Other advantages and characteristics will be seen from the followingdescription of several embodiments, provided by way of non-limitingexamples, of the fuel tank according to the invention, with reference tothe appended drawings wherein:

FIG. 1 is a schematic representation illustrating a first embodiment ofthe invention, the valve being controlled by a spring,

FIG. 2 is a schematic representation illustrating a first embodiment ofthe invention, the valve being controlled by a second float.

The invention concerns a tank (1), intended to receive fuel, andequipped with a venting system (2) for equalizing the internal pressureof the tank (1) to atmospheric pressure and avoiding any said tank.

The invention concerns a tank (1) for any type of aircraft, civilian ormilitary, such as an airplane or a helicopter for example.

In a known way, the tank (1) comprises an opening (3) providingcommunication with the exterior of said tank (1) for the ventingthereof. The venting system (2) of the tank (1) comprises a closing flap(4), mounted pivoting with respect to the tank (1) and around a pin (5)in order to adopt a closed position wherein it closes the opening (3) ofthe tank (1), and an open venting position wherein it frees said opening(3).

The flap (4) is extended at the lower part by an arm (6) that terminatesin a float (7). When the flap (4) is in the closed position, the arm (6)is essentially horizontal and in proximity to the opening (3) so thatwhen the tank (1) is full, the action of the fuel on the float (7)maintains the flap (4) in the closed position to prevent any leakage offuel through the vent opening (3).

When the level of fuel decreases, the float (7) descends together withthe level of fuel and causes the pivoting and opening of the flap (4)around the pin (5) for venting the tank (1).

According to the invention, the flap (4) comprises a valve (8) in theform of a rod (8 a) intended to ensure the venting of the tank (1) whenthe flap (4) is in the closed position and the level of fuel is belowthe threshold.

More specifically, according to a first embodiment of the invention,illustrated in FIG. 1, the valve rod (8 a) is mounted sliding within anorifice (9), in communication with the exterior, made in said flap (4).The valve rod (8 a) is capable of sliding between a position of openingand a position of closing the orifice (9). At an upper end, the valverod (8 a) comprises an upper shoulder (10) intended to act as a stop forthe closed position of said valve rod (8 a). Said upper shoulder (10)advantageously comprises an O-ring (11) for sealing the valve rod (8 a)in the closed position. The valve rod (8 a) comprises a lower endcomprising a lower shoulder (12) forming a seat for a compression spring(13), arranged around the valve rod (8 a), on the one hand pressedagainst said lower shoulder (12), and on the other hand pressed againstthe flap (4). The compression spring (13) maintains the valve (8) in theclosed position. The valve (8) is capable of adopting the open position,pushed by the force exerted by the internal pressure of the tank (1),against said compression spring (13).

In effect, when the pressure increases inside the tank (1), for examplewhen an inerting system injects inert gas into the tank (1), while theflap (4) is in the closed position by the action of the fuel on thefloat (7), due to the pitch or role of the aircraft, for example, theinjection of said gas causes an increase in the internal pressure, andthe force exerted by said internal pressure maintains the flap (4) inthe closed position, even when the fuel is no longer acting on the float(7) of said flap (4).

Thus, according to the invention, the internal pressure also exerts aforce on the valve rod (8 a) and tends to cause it to adopt the openposition. Thus, when the force exerted by the internal pressure of thetank (1) on the valve rod (8 a) exceeds the sum of the forces thatmaintain the valve rod (8 a) in the closed position, namely those forcesexerted by the atmospheric pressure and by the compression spring (13),the valve (8) is pushed into the open position, against said compressionspring (13), and ensures a venting of the fuel tank (1).

In this way, it can be seen that when the internal pressure of the tank(1) reaches a certain threshold, the valve (8) is opened and venting isensured in a secure manner

Of course, it is the compression spring (13) that determines thepressure at which the valve is to be opened (8). Indeed, the spring (13)is dimensioned to exert a force in order to maintain the valve (8) inthe closed position, said force being equal to the force exerted by thedifference between a first internal pressure threshold and theatmospheric pressure. Thus, it is possible to dimension the spring (13)so as to allow the opening of the valve (8) when the flap (4) is in theclosed position and the level of fuel is below a defined threshold, froma certain desired internal pressure threshold. Of course, a personskilled in the art will know how to dimension said spring (13) basedupon the desired internal pressure threshold.

Based upon the foregoing, when the tank (1) comprises an internalpressure above the internal pressure threshold, the valve (8) is pushedinto the open position, against the spring (13), by the force exerted bythe internal pressure, and ensures a venting of the fuel tank (1).

According to a second embodiment of the invention illustrated in FIG. 2,the operation of the flap (4) and the float (7) remain the same, eventhough the valve rod (8 a) is controlled by a second float (14). Indeed,in this embodiment, the valve rod (8 a) is not mounted sliding withinthe orifice (9) of the flap (4), but is mounted pivoting with respect tothe flap (4) around the pin (5) to adopt a closed position wherein theupper shoulder (10) closes the orifice (9), and an open venting positionwherein said valve rod (8 a) frees said orifice (9).

More precisely, the valve rod (8 a) is attached perpendicularly to asecond arm (15) extended at one end by the second float (14) andattached, pivoting around the pin (5), at another end to the flap (4).Thus, the valve rod (8 a) is capable of adopting the open position,driven in rotation by the weight of the second float (14), and theclosed position, pushed by the second float when the level of fuel inthe tank (1) reaches a certain threshold.

Thus, when the flap (4) is undesirably maintained in the closed positionby the internal pressure, and the level of fuel is below the threshold,the weight of the second float (14) augmented by the leverage effect ofthe arm (15) causes the opening of the valve (8), while the forceexerted by the internal pressure on the valve (8) is lower than the sumof the forces that tend to move the valve (8) towards the open position,namely those forces exerted by the atmospheric pressure and by theweight of the second float (14).

The internal pressure that exerts a force on the valve (8), equal to thesum of the forces that tend to move the valve (8) to the open position,corresponds to the internal pressure threshold.

In this way, in the event the flap (4) is undesirably maintained in theclosed position, venting is ensured over a range of pressures, until theinternal pressure exceeds the internal pressure threshold.

It is obvious, of course, that it is the weight of the second float (14)that determines the internal pressure threshold at which the valve (8)is moved to the closed position. Indeed, the second float (14) and thelength of the arm thereof are dimensioned in order to exert a forcetending to open the valve (8), greater than the force corresponding tothe difference between the forces exerted on the valve (8) by theinternal pressure threshold and the atmospheric pressure. Thus, it ispossible to dimension the second float (14) and the lever arm (15)thereof, such as to allow for the opening of the valve (8), when theflap (4) is in the closed position and the level of fuel is below adefined threshold, up to a certain desired internal pressure threshold.Of course, a person skilled in the art will know how to dimension saidspring (14) and the arm (15) thereof, based upon the desired internalpressure threshold.

It can be seen from the foregoing that the invention provides a fueltank capable of ensuring venting safely and under any circumstance, inorder to prevent any overpressure within said tank.

It will be appreciated that variants of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be combined intomany other different systems or applications. Various presentlyunforeseen or unanticipated alternatives, modifications, variations, orimprovements therein may be subsequently made by those skilled in theart which are also intended to be encompassed by the following claims.

What is claimed is:
 1. A fuel tank comprising a venting systemcomprising a flap for closing an opening made in the tank, said flapbeing subjected to a float and is mounted in a hinged manner in the tankso as to adopt a closed position, being pushed by the float when thelevel of fuel in the tank reaches a certain threshold, and an openventing position, being driven by the float when the level of fuel isbelow said threshold, wherein the flap comprises a valve subjected to asecond float mounted in a hinged manner in the tank so that said valveadopts a closed position, being pushed by the second float when thelevel of fuel in the tank reaches a certain threshold, and an openventing position in order to prevent overpressure within said tank,being driven by the second float when the level of fuel is below saidthreshold and the force exerted by the internal pressure on the valve isless than the sum of the forces exerted on the valve by the atmosphericpressure and by the weight of the second float.
 2. The fuel tankaccording to claim 1, wherein the second float is subjected to the valveby means of an arm forming a lever in order to increase the forceexerted by the second float on the valve.
 3. An anti-overpressure fueltank comprising: a tank; a venting system of said tank comprising: afloat mounted in a hinged manner in said tank; a flap mechanicallycoupled to said float, said flap to close an opening in said tank in aclosed flap position; a valve disposed in said flap, said valvemechanically coupled to a second float mounted in a hinged manner insaid tank, said valve comprising an open valve position to open anorifice in said flap and a closed valve position to close said orificein said flap; wherein said valve adopts a closed position, being pushedby the second float when a level of fuel in the tank reaches a certainthreshold; and wherein said valve adopts an open venting position duringthe closed flap position in order to prevent overpressure within saidtank, being driven by the second float when the level of fuel is belowsaid threshold and a force exerted by an internal pressure on the valveis less than a sum of forces exerted on said valve by an atmosphericpressure and by a weight of the second float.
 4. The anti-overpressurefuel tank according to claim 3, wherein the second float is coupled tothe valve by means of an arm forming a lever in order to increase theforce exerted by the second float on the valve.